content/releases/qpid-broker-j-9.2.1/book/Java-Broker-Runtime-Consumers.html

<!DOCTYPE html>  <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en"> <head> <meta charset="UTF-8"> <title>9.7. Consumers - Apache Qpid™</title> <meta http-equiv="X-UA-Compatible" content="IE=edge"/> <meta name="viewport" content="width=device-width, initial-scale=1.0"/> <link rel="stylesheet" href="/site.css" type="text/css" async="async"/> <link rel="stylesheet" href="/deferred.css" type="text/css" defer="defer"/> <script type="text/javascript">var _deferredFunctions = [];</script> <script type="text/javascript" src="/deferred.js" defer="defer"></script>   <meta name="go-import" content="qpid.apache.org git https://gitbox.apache.org/repos/asf/qpid-proton.git"/> <meta name="go-source" content="qpid.apache.org https://github.com/apache/qpid-proton/blob/go1/README.md https://github.com/apache/qpid-proton/tree/go1{/dir} https://github.com/apache/qpid-proton/blob/go1{/dir}/{file}#L{line}"/> </head> <body> <div id="-content"> <div id="-top" class="panel"> <a id="-menu-link"><img width="16" height="16" src="" alt="Menu"/></a> <a id="-search-link"><img width="22" height="16" src="" alt="Search"/></a> <ul id="-global-navigation"> <li><a id="-logotype" href="/index.html">Apache Qpid<sup>™</sup></a></li> <li><a href="/documentation.html">Documentation</a></li> <li><a href="/download.html">Download</a></li> <li><a href="/discussion.html">Discussion</a></li> </ul> </div> <div id="-menu" class="panel" style="display: none;"> <div class="flex"> <section> <h3>Project</h3> <ul> <li><a href="/overview.html">Overview</a></li> <li><a href="/components/index.html">Components</a></li> <li><a href="/releases/index.html">Releases</a></li> </ul> </section> <section> <h3>Messaging APIs</h3> <ul> <li><a href="/proton/index.html">Qpid Proton</a></li> <li><a href="/components/jms/index.html">Qpid JMS</a></li> <li><a href="/components/messaging-api/index.html">Qpid Messaging API</a></li> </ul> </section> <section> <h3>Servers and tools</h3> <ul> <li><a href="/components/broker-j/index.html">Broker-J</a></li> <li><a href="/components/cpp-broker/index.html">C++ broker</a></li> <li><a href="/components/dispatch-router/index.html">Dispatch router</a></li> </ul> </section> <section> <h3>Resources</h3> <ul> <li><a href="/dashboard.html">Dashboard</a></li> <li><a href="https://cwiki.apache.org/confluence/display/qpid/Index">Wiki</a></li> <li><a href="/resources.html">More resources</a></li> </ul> </section> </div> </div> <div id="-search" class="panel" style="display: none;"> <form action="http://www.google.com/search" method="get"> <input type="hidden" name="sitesearch" value="qpid.apache.org"/> <input type="text" name="q" maxlength="255" autofocus="autofocus" tabindex="1"/> <button type="submit">Search</button> <a href="/search.html">More ways to search</a> </form> </div> <div id="-middle" class="panel"> <ul id="-path-navigation"><li><a href="/index.html">Home</a></li><li><a href="/releases/index.html">Releases</a></li><li><a href="/releases/qpid-broker-j-9.2.1/index.html">Qpid Broker-J 9.2.1</a></li><li><a href="/releases/qpid-broker-j-9.2.1/book/index.html">Apache Qpid Broker-J</a></li><li>9.7. Consumers</li></ul> <div id="-middle-content"> <div class="docbook"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">9.7. Consumers</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="Java-Broker-Runtime-Flow-To-Disk.html">Prev</a> </td><th width="60%" align="center">Chapter 9. Runtime</th><td width="20%" align="right"> <a accesskey="n" href="Java-Broker-Runtime-Background-Recovery.html">Next</a></td></tr></table><hr /></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="Java-Broker-Runtime-Consumers"></a>9.7. Consumers</h2></div></div></div><p>A Consumer is created when an AMQP connection wishes to receive messages from a message source (such as a Queue). The standard behaviours of consumers are defined by the respective AMQP specification, however in addition to the standard behaviours a number of Qpid specific enhancements are available</p><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="Java-Broker-Runtime-Consumers-Prioirty"></a>9.7.1. Priority</h3></div></div></div><p>By default, when there are multiple competing consumers attached to the same message source, the Broker attempts to distribute messages from the queue in a "fair" manner. Some use cases require allocation of messages to consumers to be based on the "priority" of the consumer. Where there are multiple consumers having differing priorities, the Broker will always attempt to deliver a message to a higher priority consumer before attempting delivery to a lower priority consumer. That is, a lower priority consumer will only receive a message if no higher priority consumers currently have credit available to consume the message, or those consumers have declined to accept the message (for instance because it does not meet the criteria of any selectors associated with the consumer).</p><p>Where a consumer is created with no explicit priority provided, the consumer is given the highest possible priority.</p><div class="section"><div class="titlepage"><div><div><h4 class="title"><a id="d0e9242"></a>9.7.1.1. Creating a Consumer with a non-standard priority</h4></div></div></div><p> In AMQP 0-9 and 0-9-1 the priority of the consumer can be set by adding an entry into the table provided as the <code class="literal">arguments</code> field (known as the <code class="literal">filter</code> field on AMQP 0-9) of the <code class="literal">basic.consume</code> method. The key for the entry must be the literal short string <code class="literal">x-priority</code>, and the value of the entry must be an integral number in the range -2<sup>31</sup> to 2<sup>31</sup>-1. </p><p> In AMQP 0-10 the priority of the consumer can be set in the map provided as the <code class="literal">arguments</code> field of the <code class="literal">message.subscribe</code> method. The key for the entry must be the literal string <code class="literal">x-priority</code>, and the value of the entry must be an integral number in the range -2<sup>31</sup> to 2<sup>31</sup>-1. </p><p> In AMQP 1.0 the priority of the consumer is set in the <code class="literal">properties</code> map of the <code class="literal">attach</code> frame where the broker side of the link represents the sending side of the link. The key for the entry must be the literal string <code class="literal">priority</code>, and the value of the entry must be an integral number in the range -2<sup>31</sup> to 2<sup>31</sup>-1. </p><p> When using the Qpid JMS client for AMQP 0-9/0-9-1/0-10 the consumer priority can be set in the address being used for the Destination object. </p><div class="table"><a id="d0e9301"></a><p class="title"><strong>Table 9.1. Setting the consumer priority</strong></p><div class="table-contents"><table class="table" summary="Setting the consumer priority" border="1"><colgroup><col class="syntax" /><col class="example" /></colgroup><thead><tr><th>Syntax</th><th>Example</th></tr></thead><tbody><tr><td>Addressing</td><td>myqueue : { link : { x-subscribe: { arguments : { x-priority : '10' } } } }</td></tr><tr><td>Binding URL</td><td>direct://amq.direct/myqueue/myqueue?x-qpid-replay-priority='10'</td></tr></tbody></table></div></div><p><br class="table-break" /> </p></div></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="Java-Broker-Runtime-Flow-To-Disk.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="Java-Broker-Runtime.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="Java-Broker-Runtime-Background-Recovery.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">9.6. Flow to Disk </td><td width="20%" align="center"><a accesskey="h" href="Apache-Qpid-Broker-J-Book.html">Home</a></td><td width="40%" align="right" valign="top"> 9.8. Background Recovery</td></tr></table></div></div> <hr/> <ul id="-apache-navigation"> <li><a href="http://www.apache.org/">Apache</a></li> <li><a href="http://www.apache.org/licenses/">License</a></li> <li><a href="http://www.apache.org/foundation/sponsorship.html">Sponsorship</a></li> <li><a href="http://www.apache.org/foundation/thanks.html">Thanks!</a></li> <li><a href="/security.html">Security</a></li> <li><a href="http://www.apache.org/"><img id="-apache-feather" width="48" height="14" src="" alt="Apache"/></a></li> </ul> <p id="-legal"> Apache Qpid, Messaging built on AMQP; Copyright © 2015 The Apache Software Foundation; Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>; Apache Qpid, Qpid, Qpid Proton, Proton, Apache, the Apache feather logo, and the Apache Qpid project logo are trademarks of The Apache Software Foundation; All other marks mentioned may be trademarks or registered trademarks of their respective owners </p> </div> </div> </div> </body> </html>

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